Background/aims: There is evidence that smoking is
a risk factor for age related macular degeneration (AMD). However, not all studies have demonstrated
this association and several key questions about the role of smoking in AMD have still to be determined. The
aim of this study was to further investigate this relation for both choroidal neovascularisation (CNV) and geographic
atrophy (GA).
Methods: To investigate the relation between smoking
and the risk of developing age related macular degeneration (AMD) in white people, 435 cases with end
stage AMD were compared with 280 controls. All subjects had graded stereoscopic colour fundus photography
and AMD was defined as the presence of GA or CNV. Smoking history was assessed using multiple parameters in a
detailed questionnaire.
Results: Comparison of current and former smokers
with non-smokers was consistent with smoking being a risk factor for AMD but did not reach statistical
significance. There was a strong association between AMD and pack years of cigarette smoking (p = 0.002),
the odds ratio increasing with the amount smoked; for subjects with more than 40 pack years of smoking the
odds ratio was 2.75 (95% CI 1.22 to 6.20) compared with non-smokers. Both types of AMD showed a similar
relation; smoking more than 40 pack years of cigarettes was associated with an odds ratio of 3.43 (95%
CI 1.28 to 9.20) for GA and 2.49 (95% CI 1.06 to 5.82) for CNV. Stopping smoking was associated with reduced odds
of AMD and the risk in those who had not smoked for over 20 years was comparable to non-smokers. The
risk profile was similar for males and females. Passive smoking exposure was associated with an increased
risk of AMD (OR 1.87; 95% CI 1.03 to 3.40) in non-smokers.
Conclusions: The authors have demonstrated a strong
association between the risk of both GA and CNV and pack years of cigarette smoking. This provides support
for a causal relation between smoking and AMD. They also show an increased risk for AMD in non-smokers
exposed to passive smoking. Stopping smoking appears to reduce the risk of developing AMD.
Abbreviations: AMD, age related macular
degeneration; CFH, complement factor H; CNV, choroidal neovascularisation; GA, geographic atrophy; PED, pigment epithelial
detachment; RPE, retinal pigment epithelium
Keywords: age related macular degeneration; smoking;
case control